1. Field of the Invention
The present invention relates to a ferrite sintered body containing main components including Fe, Mn and Zn together with additives including Co, Ti, Si and Ca, and to a manufacturing method therefor.
2. Related Background Art
Ferrite sintered bodies are used as magnetic core materials in power transformers and the like. The ferrite sintered body forming a magnetic core is called a ferrite core, and Mn-Zn ferrite containing Mn and Zn is widely used. In order to reduce the amount of heat generated when the device is used, the power loss value of the ferrite core should be small across a broad temperature range (see Japanese Patent Application Laid-open No. 2005-119892). The power loss of the core is called the “core loss”.
Conventional power transformers and other devices are designed to perform at operating temperatures around 50 to 70° C., and the temperature at which power loss is minimized (hereunder called the “bottom temperature”) is 80 to 100° C. for the materials of commonly used ferrite cores. If the operating temperature of the device is lower than the bottom temperature, thermal runaway is prevented from occurring because the amount of heat generated declines gradually even if the temperature of the ferrite core rises gradually during use.
However, electronic devices and power sources have gotten smaller in recent years, and there has been strong demand for thinner and smaller transformer cores because these occupy a large amount of parts volume. Higher parts densities have also been achieved in the field of electronics. Under these circumstances, the temperature tends to rise more due to heat generation, and the temperature of the ferrite core also tends to be higher. To answer demands for higher operating temperature of electronic devices, various investigations for ferrite materials were performed (see for example Japanese Patent Application Laid-open No. 2004-35372, Japanese Patent Application Laid-open No. 2006-213532, Japanese Patent Application Laid-open No. 2006-44971).